Hydraulic power steering gear assemblies, particularly gear assemblies used to rotate the steering wheels of vehicles, particularly trucks, buses and the like, include a gear housing having a piston located in a chamber in the housing and moveable back and forth along the chamber. The piston provides a power assist to rotate the vehicle steering wheels. Check or relief valves are carried in the piston and are opened by poppet members at the ends of the cavity. The positions of the poppet members must be adjusted in order to open the valves and remove hydraulic steering assist at the end of the steering stroke, before the wheels are turned into engagement with wheel stops of the front axle.
Various types of poppet members have been used to open the relief valves. In some gear assemblies the members are mounted at the ends of the chamber and extend into the chamber to engage and unseat the valves in the piston. The poppet members are conventionally mounted in the end of the chamber using either a threaded connection or a pressed fit connection in which the members are press fitted into precise machine bores and are held in place in the bores by deformation of crush rings extending outwardly from the member.
The poppet members are adjusted in the gear assemblies by rotation of the vehicle steering wheel preferably without the necessity of performing an adjustment at the gear assembly. Also, the poppet members must be capable of repeated adjustment in the assembly, and then must hold their adjusted position during normal operation of the steering gear assembly, which may extend for many years.
Problems have been experienced with poppet members in the fitted conventional steering gear assemblies.
Poppet members which are threaded in the assembly cannot be automatically adjusted by rotating the steering wheel. Adjustment requires that a worker manually rotate the members in the gear assembly.
The pressed fit deformable metal type poppet members can be automatically adjusted using the steering wheel only, but lose their ability to maintain adjustment if their position has been adjusted a number of times. This is because these device are held in place by a pressed fit connection and movement or adjustment of the devices degrades the connection so that the devices are no longer held tightly in place. Further, the pressed fit devices require precision machining of the passage, adding to the expense of manufacture of the gear assembly.
Also, with press fit type poppet members, the members are extended toward the chamber prior to adjustment by extending a tool into the passage and tapping the device inwardly. This operation can easily result in a worker pushing the device entirely through the passage and into the chamber, where it disrupts operation of the gear assembly. The gear assembly must be taken apart to remove the poppet device.